Questions tagged [captcha]

Captcha is a type of challenge-response test used in computing as an attempt to ensure that the response is given by a human being and not generated by a computer.

CAPTCHA is an acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart".

A CAPTCHA or Captcha is a type of challenge-response test used in computing as an attempt to ensure that the response is not generated by a computer. The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade.

Because other computers are supposedly unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Thus, it is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine.

The usual reason for using a CAPTCHA is to prevent automated spam from being posted into a public discussion forum or similar site.

A common type of CAPTCHA requires the user to type letters or digits from a distorted image that appears on the screen. However these are becoming increasing unreliable as the automated spam systems that they are trying to defeat are becoming much better at reading the distorted text. More advanced CAPTCHAs are thus becoming available that require the user to answer more detailed questions or perform more complex actions.

Most CAPTCHAs, particularly the more difficult ones, suffer from accessibility issues. The act of making it difficult for an automated system to read and respond to the CAPTCHA also makes it more difficult for many users with disabilities to access sites that use them. For example, a user who relies on a screen reading web browser may be unable to see the CAPTCHA image. Better CAPTCHA systems will provide solutions to some of these issues, such as an audio alternative, but these users are generally still left at a disadvantage.

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Qaptcha - is it effective?

See the demo of JQuery Qaptcha here - http://www.myjqueryplugins.com/QapTcha/demo It requires you to slide the slider to unlock and prove you're human. I've read all about how it's setting random field values and erasing them, but isn't all that…
Shane N
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What is the best/recommended CAPTCHA component for ASP.NET

Does anyone have any recommendations for CAPTCHA components for use in ASP.NET projects?
flalar
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How do I set up Scrapy to deal with a captcha

I'm trying to scrape a site that requires the user to enter the search value and a captcha. I've got an optical character recognition (OCR) routine for the captcha that succeeds about 33% of the time. Since the captchas are always alphabetic text, I…
Sushil
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Client Server REST API captcha implementation

I'm building client server REST application. Client side is based on Angular while server is PHP (not that it matters much anyhow). What I am wondering if there are any best practices, good examples of captcha implementation in this case? Captcha…
Vladimir Cvetic
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Will an English CAPTCHA be an issue for people in other countries?

What if I have a captcha that displays a series of English characters. Will people who don't speak English have trouble interpreting and/or typing these characters? If this is the case then what is the best solution for an internationalized…
rook
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Most effective form of CAPTCHA?

Of all the forms of CAPTCHA available, which one is the "least crackable" while remaining fairly human readable?
Yes - that Jake.
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How to unit test a form with a captcha field in django?

I would like to unit test a django view by sumitting a form. The problem is that this form has a captcha field (based on django-simple-captcha). from django import forms from captcha.fields import CaptchaField class ContactForm(forms.forms.Form): …
luc
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How CURL Login with Captcha and Session

define('COOKIE', './cookie.txt'); define('MYURL', 'https://register.pandi.or.id/main'); function getUrl($url, $method='', $vars='', $open=false) { $agents = 'Mozilla/5.0 (X11; U; Linux i686; en-US) AppleWebKit/534.16 (KHTML, like Gecko)…
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reCAPTCHA triggering Java warning in IE

We recently added reCAPTCHA 2.0 to our site and now we're occasionally getting a message from IE about Java. Here is the message: The page you are viewing uses Java. More information on Java support is available from the Microsoft website. Our…
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New Google reCAPTCHA JavaScript namespace callback

We're trying to implement the new Google reCAPTCHA on our website, however when we try and load a callback from it using a namespaced function, the callback does not run. Changing the callback to not use a callback works correctly. We're doing…
Toby
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What CAPTCHA system is compatible with ASP.NET MVC?

What CAPTCHA system is compatible with ASP.NET MVC? Are there any good examples out there?
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How do I add a CAPTCHA to my PHP form?

My knowledge of php is not good and I need help. I have this php form but I don't know how to add a CAPTCHA mechanism. How do I achieve this?
php form
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Integrating Captcha with Spring Security

What is appropriate way to integrate SpringSecurity with Capcha ? I have following use case : When user will tries to login, if we he failed to login N times, captcha will be displayed, so authentication will be using three parameters : username,…
Pavel Rodionov
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How could we integrate the Captcha in iOS application?

I googled for integration of Captcha in iOS app but do not found any relevant way to do so. Even i sign up with reCAPTCHA and searched whether the plugins for Captcha are available for iOS or not? I didn't found any plugin for iOS there. Somewhere…
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How to use Python plugin reCaptcha client for validation?

I want to make a captcha validation. I get the key from the recaptcha website and already succeed to put the public key to load the webpage with the challenge.